1. Field of the Invention
The present invention relates to a method of making an oxygen scavenging sealant composition that can be utilized to improve the shelf life of packaged materials, such as oxygen sensitive foods. As used herein, the term sealant is as known to those skilled in the art for forming an hermetic seal with a packaging container. It includes, for example, gaskets (bonded) and liners (non-bonded).
2. Description of Related Art
In packaging oxygen sensitive materials such as food, beverages and pharmaceuticals (collectively "foodstuffs") oxygen contamination can be particularly troublesome. Care is generally taken to minimize the introduction of oxygen, to exclude the oxygen from the package when initially sealed or to otherwise reduce the detrimental or unwanted effects of oxygen on foodstuffs.
It is known to package foodstuffs in containers wherein the walls contain an oxidizable component which reacts with oxygen that is trapped in the package or permeates through the wall of the package. These systems are described, for example, in U.S. Pat. Nos. 4,536,409 and 4,702,966.
When the container wall is formed of a glass or metal body and is provided with a metal closure, oxygen does not permeate through the container walls due to the impermeable materials used to make the container walls or closure. However, it has long been recognized that conventional containers employed for the storage of oxidizable materials may be permeable through the seams at the juncture between glass or metal components, often through sealants used to fill these seams. In addition, oxygen may remain within the container from the closing operation.
To extend the shelf life of foodstuffs while continuing to utilize conventional materials, attempts have been made to incorporate oxygen scavenging systems in the container crown or closure. For example, U.S. Pat. No. 4,279,350 discloses a closure liner which incorporates a catalyst disposed between an oxygen permeable barrier and a water absorbent backing layer.
U.S. Pat. No. 4,510,162 describes an oxygen adsorbent composition containing iron particles, yeast and moisture, which is mounted on a suitable carrier and adapted to be mounted in a closable container for removing oxygen therefrom.
U.S. Pat. Nos. 4,756,436 and 5,106,886 disclose an oxygen scavenging composition to be installed as a gasket between the cap and the container. Particularly, U.S. Pat. No. 5,106,886, discloses a sealant that incorporates a sodium ascorbate oxygen scavenger in a plasticized polyvinyl chloride.
A disadvantage associated with the prior art oxygen scavenging sealant compositions is their inability to maintain a hermetic seal over a prolonged shelf life.
To overcome this disadvantage, it is an object of this invention to provide a method for compounding an oxygen scavenging sealant composition having improved long term sealing ability, thereby preventing the oxidation of the foodstuff and prolonging the shelf-life of the package.
Another object of the invention is to provide a method of compounding an oxygen scavenging sealant composition that has an improved oxygen uptake.
Other objects and aspects of the present invention will become apparent to one skilled in the art on a review of the specification and claims appended hereto.